Technical Field
The present subject matter relates to a method to control an on board unit (OBU) within a communication zone of a road side unit (RSU). Said OBU can be set into an active mode and a sleep mode. In said sleep mode the electronics of said OBU may thereby be shut down, such that no or a minimum of power is consumed. The OBU is set into said active mode when said OBU is entering said communication zone, whereby a communication unit of said OBU thereby is powered such that the OBU can communicate with said RSU. The subject matter further relates to an on board unit capable of communicating with a road side unit.
Background Art
Electronic Fee Collection (EFC) stations and related systems, sometimes called road side stations comprises road side units (RSU) that may communicate with an on board unit (OBU) located in a vehicle. When the vehicle approaches an RSU the OBU is activated upon reception of a certain wake-up command that is sent from the RSU in order to perform a transaction. The transaction may be payment for the toll and/or an access transaction where the RSU opens a gate or similar for the vehicle to pass through. Even if the transaction only takes place in a specific zone close to the RSU the OBU is active from the moment the OBU is within range to be activated by the RSU until the moment the OBU receives a release command from the RSU.
It may further be desirable to determine the position of the OBU, and thereby of the vehicle. For this purpose various means of localization features in an RSU may exist that based on a received signal from the OBU can estimate the OBU's location. Hence, for systems where it is desired to also know the location of a vehicle outside the actual zone of data exchange that is needed for the transaction itself there is a need to get the OBU to send arbitrary data in data frames called tracking frames that the RSU can use for localization means. This inherently means that the OBU consumes a lot of power idling while waiting for a command from the RSU to send such a tracking frame. For an OBU that is battery powered this severely reduces the battery power and thereby reduces the time the OBU can be used before the battery is drained.
There is thus a need for an improved method of controlling an OBU by an RSU.